Miami Beach, Champlain Towers South apartment building collapse, Part 02 151

[dik]

thread815-484587


Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Jerehmy]

I just have a few thoughts:

1. Its very unlikely the penthouse, even if unaccounted for (which isn’t likely, as a recent interview indicated it was accounted for), to cause a failure. I agree with XR250 that the majority of the floors were likely no where near their design loads.

2. The complete degloving of rebar is very concerning and makes me question the ductility of older reinforced concrete structures. There could be many reasons for this degloving; I don’t know how much how quickly a load is applied effects this, significant rust or millscale on the rebar, etc.

I always thought that if you develop rebar, it should yield significantly prior to pulling out (if it all). Even in the video you can see 20’ sections of columns falling down like a toppled jenga. Nothing in the video looked like a ductile failure. I looked at photographs from northridge and saw similar rebar completely devoid of concrete.

3. All the photographs of the concrete columns I saw did not show a level of visible degradation that you’d expect to cause failure. If there was severe corrosion of rebar, there’d be spalling in those locations. So theres unlikely to be any significant hidden damage.

 

[NOLAscience]

IMO, that was a little EARLY to close the opening discussion.

I meant early in "time", not early regarding number of posts

UNVERIFIED INSPECTION REPORT
Professional engineer Frank Morabito went into 68 of the units a couple of months before October 2018 inspection (between August and September of 2018). It sounds like 68 of the owners/renters were unhappy with the board's inaction on what they thought was evidence of serious damage. They hired the engineer for an assessment, and then the board had to follow-up with a full structural inspection and report. But time was not on their side.

THE April 9 2021 WODNICKI LETTER (76 days before collapse): The board recognized that the situation was serious, but they had ultimately lost too much time with political and financial issues.

THE OTHER CHAMPLAIN TOWERS
See photo at 3Engr1888 @ 27 Jun 21 03:04
Champlain Towers North is "Temporarily closed" as per Google Maps, 11:53 am 6/28. North seems to have a similar penthouse:

https://www.miamicondoinvestments.com/champlain-towers-north-condos

East, built ca 1994, seems to NOT have a penthouse, built ca 1994

https://www.miamicondoinvestments.com//champlain-towers-east-condos

These residents at EAST should also evacuate until that damaged column in the basement parkcade is shored up. Not 'repaired'. I'm assuming there were no changes to the footprint at North and East like the change at South that hetgen noted @ 26 Jun 21 11:25

FOOTPRINT REVISED

Responding to Ingenuity's post, please correct me if I'm wrong, but it seems column I-10 was originally designed as an interior column. At some point the decision was made to not construct this extension, making column I-10 an exterior column. Depending on how late in the game this decision was made, makes me wonder if it was ever analyzed for the increased live load distribution? Or was it simply a matter of "it's carrying less trib, therefore OK" ....then add in the planters installed on the corroded plaza-level slab. Is it possible the column was overloaded?

I'd like to see a single comment with the drawings of the garage, lobby, and the first full residential floor before the footprint was revised and after. I tried scrolling up and down to compare, but I'm too tired to do that tonight. Was this one column that was supposed to be within the building envelope exposed to the elements at ground level? Can you see this column in photos?

TIDES/HIGH WATER
The high tide on Wednesday/Thursday is interesting.

WOMAN BOUGHT UNIT IN DECEMBER; ANGRY AT UNDISCLOSED STRUCTURAL PROBLEMS
Unit 611: Monteagudo, age 50s
“I ran and tried to close it [window] but I couldn’t, I imagine because it was unlevel already because of all the movement,” she recounted. “I heard a crack and when I looked, I saw a crack traveling in the wall two fingers thick. Something told me, you need to run.”
She purchased unit 611 in December; was upset when she learned of structural issues after the sale. Extra $1000 special assessment was to start in July.

VALUE OF 40 YEAR OLD HIGH RISE CONDOS
I want to say that it seems to me that the value of a high-rise condo building built near the coast after _______ goes to zero at about 40 years, and this should be reflected in its price when it is sold at, say, 30 years. But this particular building seemed to have more problems than most, so idk.

That's about enough for tonight.

 

[spsalso]

Let us assume a floor to floor spacing of 10'. Let us assume that spacing suddenly changes, on the bottom most floor, to 20'. Would that be a problem for the vertical columns involved? Would it be a problem if the rebar arrangement had not accounted for a lack of horizontal support at the midpoint of this "new" column height?

Again, a timeline of this event will be very interesting.


spsalso

 

[IEGeezer]

1. Its very unlikely the penthouse, even if unaccounted for (which isn’t likely, as a recent interview indicated it was accounted for), to cause a failure. I agree with XR250 that the majority of the floors were likely no where near their design loads.

I agree that you are making a fair point. My concern is more about safety margins being on the thin side. Stuff happens. If your safety margins are a little thin, it may make the difference between something repairable and something that isn't. However, a better question may be: Why didn't it occur to someone to shore things up? Here we go again. The FIU pedestrian bridge was failing structurally and nobody thought to shore it up.

You can't snap your fingers when making structural repairs, but surely it can't hurt (except your pocketbook a little) to do some shoring.

 

[epoxybot]

It's not that Florida didn't have a Building Code, it is just that, before Hurricane Andrew, Cities & Counties had a very Libertarian application of the code. All that changed following Hurricane Andrew.
All over the US, up to the 80's Cities & Counties were quite parochial in attitude towards State Mandated Building Codes. That remained so in states like Florida & Texas, as stand outs.

 

[lucky555]

Present day Florida Building Code - have the requirements updated after Andrew to incorporate any rebar corrosion protection? Plain rebar in ocean side construction, with constant chloride exposure, it just seems like a bad idea.
Even in Canada with road salt, we use cathodic protection, rebar coatings in bridge decks, galvanized or epoxy. Better than nothing.

"Re-certification" every 40 years, it could be inspections every year and it would change nothing. The HOA can still sit on findings and do nothing.
It frustrates me that engineering is surrounded by non-engineers calling the shots, whether it's sneaking in a penthouse, a construction contractor doing improv to save a few bucks, or a condo board not moving on critical repairs and in 2021 deciding "let's replace the roof" as the priority.

 

[Murph 9000]

"Re-certification" every 40 years, it could be inspections every year and it would change nothing. The HOA can still sit on findings and do nothing.

A better inspection regime can include enforcement. Catching the problems earlier makes them less costly (CTS was going past an average of $100k per apartment, which is a big problem for getting the owners to pay), and less urgent (they can take their time, but still have some sort of enforcement deadline). Get the code enforcers to give priority to safety issues instead of whether the sea turtles are upset by the type of lights.

Yes, stuff will probably still slip through the cracks with more frequent inspections, but finding and monitoring the problems is essential to reducing the risk. The FIU structural engineering professor that was talking about this was suggesting different tiers of inspection over time. You could have a quick annual walkaround to just note problems, 5 year basic inspections of the major stuff, 10 year inspections that get into more without being too disruptive, and 25 year inspections that involve tearing stuff out for a proper look. The thing that's certain is that 40 years is much too long for regulatory inspection.

If the HOA is faced with their property value going to zero via some sort of red tag condemnation, as the final step of enforcement, they will do what is needed to stay ahead of that.

 

[jrs87]

Any comments about the Proflex membrane material depicted in this photograph? Below the failed level the ProFlex is on, the edge of another failed level can be seen.

 

[Murph 9000]

Any comments about the Proflex membrane material depicted in this photograph?

A quick search suggests they do all sorts of products for different purposes, so difficult to say for certain. That is a fallen floor slab which has remained attached to the elevator shaft shear wall, hinged down on its rebar. It would have been the floor of a bedroom. It may be something quite innocuous like an underlay for flooring material.

 

[Murph 9000]

I had what could be a great idea. Restaurants have to display a hygiene / safety rating in their window / entrance. Do the same thing for all large buildings (condos, hotels, offices, venues; anywhere that commonly has a large number of people in it); based around maintenance, safety, and code compliance. I doubt I'm the first to think of it, and it basically expands existing red tag unsafe building notices. Importantly, it could cover more than the all or nothing with red unsafe notices, making it clear when a building is gradually deteriorating, before it gets to a critical level. Just don't make it about lights upsetting sea turtles.

Label them clearly, and it will hit them in the pocket if they have a bad rating. Let people lookup the outstanding defects and violations on the town / city website. It could potentially turn the situation fully around and have the residents pressuring the HOA to keep an A rating, so their value is maintained and insurance rates kept low. It even goes beyond monetary value, by preventing people taking advantage of false prestige from a beautiful lobby that disguises a wreck of a building.

 

[Mbrooke]

Does anyone have the original 1979 blueprints to the tower?

 

[Murph 9000]

Does anyone have the original 1979 blueprints to the tower?

You'll find the original 1979 plans and various other things here:

https://townofsurfsidefl.gov/depart...erk/champlain-towers-public-records-documents

N.B. There are multiple versions of the original plans in the big 1979 PDF, and some are for the North tower.

 

[OHIOMatt]

Since I became aware of this tragedy, last week, I have followed as closely as possible. I have numerous thoughts on the state of the industry that I use to earn a living and take care of my family.

The 40 year recertification requirement is actually more stringent than most jurisdictions. In my home jurisdiction, commercial buildings are provided with a certificate of occupancy upon the completion of construction. At this point, the local building official cedes jurisdiction to the fire chief. The subsequent inspections focus almost exclusively on fire hazards, egress paths, and fire suppression. The structural systems are never evaluated again, unless somebody sees an obvious issue.

ICC publishes the "International Existing Building Code" and the "International Property Maintenance Code". Neither of these codes have been adopted by my home state. By default, once a certificate of occupancy is awarded, there is no oversite by an government body.

The concept of Qualified Immunity for building officials needs to re-evaluated. Typically the Chief Building Official is a registered professional (but this is not a requirement, maybe it should be).

Perhaps the way we have always done things is needs to change. I think, that the public has a vastly inflated view of the capabilities and responsibilities of the building department. In my experience, with a few exceptions, they rarely provide any value in the plan review process, especially when it comes to the structural design. Maybe we need to rethink this process entirely. I have done quite a few projects were the owners insurance carrier required conformance to the design standards of FM Global. Often in these cases, the review is more robust and any comments seem justified by their design standards. Perhaps requiring a 3rd party review would reduce design errors. In addition, these buildings typically get inspected on a routine basis, as the insurer does not want to pay a claim. Maybe the people that would be financially responsible for the collapse would take a greater interest in the building than someone with qualified immunity.

Our engineering boards seem to be very slow and hesitant to act, even in cases where there is ample evidence of violations of the laws and rules. Two cases recently, the hotel collapse in New Orleans and the bridge collapse in Florida standout. The last time I checked, the engineers in both of those case are still practicing and still licensed. I am not suggesting, at this time, that this tragedy is the result of an engineering error or a judgement error by any engineer. Since our industry is self governing, oversite and discipline by the board has to occur when engineers commit a violation.

Hopefully something positive can come out of this tragedy.

 

[Mbrooke]

Found them, thank you very much Murph 9000!

https://www.townofsurfsidefl.gov/do...-collins-ave-1979-plans.pdf?sfvrsn=bd2a1194_2

 

[799931]

Agreed.

 

[JStructsteel]

Im reading alot about the pool. How is that an issue since its not near the building? The corbel at the deck failed, causing the pool deck to collapse, and then leave the building columns un-braced, causing the building to fail?

Another question, will this failure cause you to think more about how you word an inspection report?

 

[Trenno]

I'm curious about the lack of shear walls (isolated and composite) and the impact it may or may not have had on the collapse. If they had closed off the secondary stair with the red walls, would that have prevented the total collapse between Grid H - P, assuming the diaphragm were cut off from the blue shear walls if the initial collapse occurred around Grid H.

Running a few quick numbers on the East-West direction:
Building is 46m wide and 36m above ground = 1656m^2. Say 2.5 kPa basic ULS wind pressure (hurricane)
Base Shear = 1656 x 2.5 x 1.3 = 5400 kN
Base Moment = 2.5 x 1.3 x 46 x 36^2 x 0.5 = 96 900 kNm
So they have two 2.5m long by 250mm (27.5 MPa) shear walls in the EW direction with not much gravity load due to openings either side.
Tens/Comp stress at the ends of shear walls would be running at around 185 MPa
(ie over 6 times the concrete grade) (not taking into account at effective flange action with the long transverse wall)...

Column on Grid I/8 is 305mm x 610mm (incorrectly noted as Type G but actually Type L) with 41.4 MPa concrete grade. Length is around 4.2m at the lobby with a slenderness ratio Le/r of say 1.0*4200 / 0.3*305 = 46 (>25 so deemed slender)
Say design ULS loading of 10 kPa (200mm slab, 1 kPa SDL, 2 kPa LL) with roughly 50m^2 trib area over 12 floors is around 6000 kN.
ULS stress is then running at around 32.2 MPa (78% of f'c).
At that sort of slenderness I'd be expecting a max ULS stress of roughly 30% of f'c.

I might be way off with my imperial to metric conversions...

 

[ash060]

Saw a article from CNN written by an architect

Link

Surprised that he would comment on structural aspects of the building. Should engineers be speaking up?

 

[Zroge]

@JStructsteel
It may not be an issue at all. Attention is being given to the pool for two reasons.
1 - The most recent pre-collapse photos of the basement garage were from the pool room. We don't know if that level of damage extended to the rest of the basement but we can't rule it out.
2 - Pool chemicals can degrade both concrete and metal, its known that there was standing water in the pool room so it would stand to reason pool water was leaking into the garage. While it would be a small
amount, its possible chemicals worked their way into the columns under the building itself accelerating the damage from salt water that we know was there in 2018.
At this point its all speculative. We may learn tomorrow that 2x4s were being duct taped over cracks which would take the conversation in an entirly new direction (i'm in no way saying this was the case, just using it as an extreme example). So why not discuss the possibility that poor pool maintenance lended itself to the collapse?

 

[ajk1]

I do not know to what extent rebar corrosion may be a significant factor in the collapse, but am somewhat doubtful, unless there are areas where the deterioration is much more than the photos that I have seen to-date, although I did see one photo where the delaminatio was horrendous.
I have seen lots of rebar corrosion and resulting concrete spalling in parking garages here in Ontario, where large amounts of corrosive deicing chemicals are used on winter roads and tracked into parkig structures, including parking structures directly below high rise buildings--yet they did not fall down (except the Algo Mall)


I think all possible causes should be considered at the outset, and then whittled down by careful examinaion and consideration of the evedance, examinanation of drawings and site review reports during construction, possible design and constructin errors, deterioration, foudation problems, etc.

Geotechnical and structural engineer should be involved in the review of the case. Could this be s fundation filuer?
What type of foundation did it have? Was it proprly installed?

I would conider immediately, withou delay, evacuating and tmporarily relocating the people in the buildings similarly designed, and consructed by this developer/contractor/engineer/architect at that time.

What did Einstein say? - "The definition of insanity is doing the same thing repeatedly and epecting a different result".

If there is another buiding of the same design, by the same developer/contrator/construction manager/architect, in similat exposure conditions and similar age, then I woud expect the same result eventually- i.e. collapse.
anout

Some type of monitoring system should be installed as soon as possible without delay in the remaining budings of this design if people are to return to them.

Some of the commentary in the media (TV, etc.) is poor, but some by experienced structural engineers has been good.

I would be interested to know if the slabs were prestressed, or not, and if they were was it with unbonded tendons?


Full disclosure - I waa involved from 1983 to 1997 with preparation of the Canadian Standards Asoociatio(CSA) Stanard S413, Parking Structures which deals substantially with corrosion and how to protect against it. Type and class of concrete, protective systems, drainage, etc.